Catheters may be introduced into the human body as part of diagnostic or treatment procedures. Such devices are typically introduced through arteries and are advanced to the site designated for diagnosis or treatment, which site may be a particular vessel or an organ, for example, the heart. In certain uses, a technique for advancing a diagnostic or treatment catheter and guidewire requires opening of a Tuohy-Borst connector, moving the catheter to the designated site within the body where diagnosis or treatment is to occur, and reclosing the connector, all of which steps are well known to skilled clinicians.
The aforementioned practice presents a number of difficulties. If the Tuohy-Borst connector is overtightened on reclosure, subsequent catheter movement and manipulation may be impaired. Also, closure is not reliable for the entire range of diameters of catheters which may be used, especially with respect to small diameter catheters, for example, those used in percutaneous transluminal coronary angioplasty ("PTCA") procedures, which make positive sealing closure of the Tuohy-Borst connector difficult. Further, known devices require the Tuohy-Borst connector to remain open while the catheter is manipulated which results in undesirable backbleed from the blood vessel when the catheter is introduced into the patient's vasculature through the connector. The backbleed may continue for an extended period of time while the catheter is being positioned, often causing complications in the PTCA procedure, and even conceivably, resulting in considerable loss of blood for the patient. The rate of backbleed is inversely related to the outside diameter of the catheter and relative to the fixed diameter connector so that as the catheter shaft diameter decreases, the rate of backbleed increases.
One known device for controlling backbleed while positioning an over-the-wire or fixed-wire catheter is described in U.S. Pat. No. 5,203,774 to Gilson et al., incorporated herein in its entirety. This device consists of a rigid sleeve assembled over the shaft of a catheter and shaped to fit into a Tuohy-Borst connector. The sleeve has an external diameter chosen so that when the connector is closed, a seal is formed between the sleeve and the connector, while still allowing for free movement of the catheter shaft in relation to the closed connector and for free movement of the guidewire housed within a lumen of the catheter. Backbleed is limited to the annulus between the inner diameter of the sleeve and the outer diameter of the catheter, diameters which are chosen to be complementary to minimize backbleed without compromising catheter movement. A disc-like flange or head is provided at the proximal end of the sleeve to limit axial motion of the sleeve within the connector.
On occasion, there is a need to exchange one catheter for another. For example, where only a very small balloon dilatation catheter can cross a stenosis, a pre-dilatation catheter may be used to partially dilate the stenosis so that a larger balloon dilatation catheter can be exchanged therefor and positioned across the stenosis to restore the vessel to a more natural, non-occluded diameter. It is difficult to perform a catheter exchange with an over-the-wire type catheter, the only type which may be used with the device disclosed in the '774 patent, because the operator must ensure that the guidewire remains in place across the stenosis while the shaft is being withdrawn. An extension guidewire, whose overall length is approximately the length of the balloon catheter, is attached to the proximal end of the guidewire prior to withdrawing the shaft so that the operator has a sufficient length wire to hold onto as the catheter is withdrawn and envelopes the proximal end of the guidewire. Guidewires with proximal ends that are suitably adapted to receive an extension guidewire are described in U.S. Pat. Nos. 4,917,103, 5,031,636 and 4,922,923 to Gambale et al.
The need for an extension wire and the difficulties associated with the exchange procedure using an over-the-wire type catheter are avoided when a "monorail" type catheter is used in lieu of the over-the-wire catheter design. The "monorail" catheter has the guidewire external to the shaft for most of the shaft's length. See U.S. Pat. No. 4,762,129 to Bonzel, the entire disclosure of which is incorporated herein, for an exemplary "monorail" type catheter. The guidewire is slidably received in an abbreviated or shortened lumen which extends only from the distal tip of the catheter to a more proximally located opening along the catheter shaft. This opening is sometimes referred to as an "exchange joint." This shortened lumen is typically between three and forty centimeters long. After a conventional length angioplasty guidewire has been advanced to the site of the stenosis, the monorail catheter can be threaded onto the externally extending proximal portion of the guidewire and introduced to the patient's vascular system through the Tuohy-Borst connector. The monorail catheter is then advanced through the guide catheter and beyond, alongside the guidewire with only its distal segment attached to and guided by the guidewire. The proximal portion of the catheter and the guidewire separately extend through the Tuohy-Borst connector in this procedure.
Previous to this invention, there was no device which would satisfactorily control backbleed out of a proximal connector or fitting yet also provide for a guidewire which extends proximally alongside a catheter, as in the monorail catheter design. Further, previous designs have required the operator to manually hold the guidewire in position during catheter manipulations and the like. There is a need for a device, heretofore unavailable, which provides backbleed control during and after placement of a monorail type catheter within a patient's vascular system, and which provides selective clamping of a guidewire for all varieties of catheters useful for diagnostic or treatment purposes.